1. Field of the Invention
The present invention relates in general to an air cleaner having an air pollution level sensor, and more particularly to a method for controlling the amount of wind for air-cleaning regardless of an initial air pollution level sensed by the air pollution level sensor in the air cleaner.
2. Description of the Prior Art
Referring to FIG. 1, there is shown a schematic block diagram of a conventional air cleaner. As shown in this drawing, the conventional air cleaner comprises a sensor 1 having a heating coil 2, electrodes 3 and a variable resistor 4, for sensing an air pollution level, a microcomputer 5 for outputting a wind amount control signal in response to an output signal from the sensor 1 corresponding to the sensed air pollution level, and a blower 8 for generating a desired amount of wind for the air-cleaning in accordance with the wind amount control signal from the microcomputer 5. The variable resistor 4 functions to adjust sensitivity of the sensor 1.
The operation of the conventional air cleaner with the above-mentioned construction will hereinafter be described.
Upon powering on the air cleaner, the sensor 1 is supplied with a DC voltage Vcc (about +5 V). Then in the sensor 1, the heating coil 2 is heated and a voltage based on the heating of the heating coil 2 appears between the electrodes 3. The variable resistor 4 cooperates with the electrodes 3 to divide the +5 V DC voltage Vcc and applies the divided voltage to the microcomputer 5.
For example, provided that the air pollution level is increased, the voltage between the electrodes 3 drops abruptly and the voltage across the variable resistor 4 rises to the contrary. The increased voltage across the variable resistor 4 is applied to an input terminal I1 of the microcomputer 5. In response to the increased voltage across the variable resistor 4 inputted therein, the microcomputer 5 recognizes that the air pollution level is increased and outputs the wind amount control signal in accordance with the increased air pollution level. As a result, the blower 6 generates a desired amount of wind for the air-cleaning based on the wind amount control signal from the microcomputer 5.
Thereafter, when the air is cleaned and, the air pollution level becomes low, the voltage between the electrodes 3 is increased and the voltage across the variable resistor 4 is reduced to the contrary. The reduced voltage across the variable resistor 4 is applied to the input terminal I1 of the microcomputer 5. In response to the reduced voltage across the variable resistor 4 inputted therein, the microcomputer 5 recognizes that the air pollution level is reduced and outputs the wind amount control signal via output terminal O1 in accordance with the reduced air pollution level. As a result, the blower 6 decreases the amount of wind based on the wind amount control signal from the microcomputer 5.
Referring to FIG. 2, there is shown a flowchart illustrating a system program stored in the microcomputer 5 in the conventional air cleaner of FIG. 1. Upon powering on the air cleaner, it is checked whether a reference value of the air pollution level has been defined. If the air cleaner has not been powered on, the system program returns to an initial state. Herein, the reference value means an initial value of the air pollution level sensed by the sensor I after powering-on of the air cleaner.
If the reference value of the air pollution level has been defined, the defined reference value of the air pollution level is compared with a present air pollution level being provided by the sensor I with the lapse of the time. Obtained in accordance with the compared result is an increment of the air pollution level.
If the reference value of the air pollution level has not been defined, the system program defines an initial value of the air pollution level provided by the sensor 1 as the reference value and then returns to the initial state.
When the increment (referred to hereinafter as .increment.PPM) of the air pollution level is smaller than 3, the blower 6 is deactivated. If the .increment.PPM is greater than or equal to 3 and smaller than 6, the blower 6 is activated to generate one-stage amount of wind. If the .increment.PPM is greater than or equal to 6 and smaller than 9, the blower 6 is activated to generate two-stage amount of wind larger than the one-stage amount of wind. If the .increment.PPM is greater than or equal to 9 and smaller than 12, the blower 6 is activated to generate three-stage amount of wind larger than the two-stage amount of wind. Also, if the .increment.PPM is greater than or equal to 12 and smaller than 15, the blower 6 is activated to generate four-stage amount of wind larger than the three-stage amount of wind. Finally, when the .increment.PPM is greater than or equal to 15, the blower 6 is activated to generate five-stage amount of wind as the maximum amount. In this connection, the amount of wind generated by the blower 6 can be defined in the following order: EQU 1-stage&lt;2-stage&lt;3-stage&lt;4-stage&lt;5-stage (1)
As mentioned above, in the conventional air cleaner, the initial value of the air pollution level sensed by the sensor 1 is defined as the reference value and the increment of the air pollution level is obtained by subtracting the reference value from a present air pollution level being provided by the sensor 1 with the lapse of the time. Then in accordance with the increment of the air pollution level , the blower 6 is activated to generate one of the 1-stage to 5-stage amount of wind. Namely, the more the increment of the air pollution level is, the generated amount of wind is increased.
However, the conventional air cleaner is desirable in the place of relatively low air pollution level such as houses and offices, but has a disadvantage in the place of relatively high air pollution level such as underground shopping arcades, factories and public places crowded with many people. In other words, the relatively high air pollution level has been present in the factory from powering-on of the air cleaner. For this reason, a great amount of wind must be generated just from powering-on of the air cleaner. However, according to the conventional air cleaner, the initial value of the air pollution level sensed by the sensor 1 is defined as the reference value and much amount of wind is not generated until the increment of the air pollution level is considerably large. Moreover, when the increment of the air pollution level is considerably large, the amount of wind will, in fact, be required more for the air-cleaning in the factory than that of wind generated from the air cleaner at that time. That is, in the case where the conventional air cleaner is employed in the place of relatively high air pollution level, it cannot perform an efficient air cleaning because too high value is defined as the reference value.